1. Field of the Invention
The present invention relates to an apparatus and method for changing a channel in a digital broadcasting system, and more particularly, to an apparatus and method for changing a channel in a digital broadcasting system that can reduce a channel change delay which occurs when there is a channel change request from a user of a digital broadcasting service provided through an IP (Internet protocol) network.
2. Description of the Related Art
In digital broadcasting, program information of respective channels based on a coding standard such as moving picture experts group (MPEG) is compressed with high efficiency, and programs corresponding to a plurality of channels are multiplexed with high efficiency based on a digital modulation method of a transmission media and then transmitted. Thus, digital broadcasting, unlike analog broadcasting, can be performed over tens to hundreds of channels without using numerous repeaters.
Digital broadcasting is classified according to transmission medium into digital terrestrial broadcasting, digital satellite broadcasting, and cable digital broadcasting. Digital satellite broadcasting is currently spreading all over the world, and digital terrestrial broadcasting is being tested in some places such as the USA and Europe.
Digital broadcasting has been mainly provided via cable. However, with the development of high-speed Internet technology, it is starting to be provided via an IP network.
A digital broadcasting system for providing such a digital broadcasting service includes a digital broadcast server for providing broadcast data through an IP network, and at least one set-top box connected to the IP network to receive the broadcast data provided from the digital broadcast server and present it to a user.
The digital broadcast server encodes analog broadcast data received from a digital broadcasting station (i.e., system operator), converts it into digital broadcast data, compresses it to generate packets, and multi-casts the packets to the IP network. Here, the packets sent to the IP network can be formed according to a moving picture experts group 2 (MPEG-2) transport stream (TS) standard.
That is, the digital broadcast server transmits the broadcast data of a certain channel to the IP network through a multi-casting transmission.
The set-top box decompresses and decodes the packets received from the IP network and then provides the digital broadcast data to a digital television.
Here, a multi-cast packet transmitted from the digital broadcast server to the IP network contains only broadcast data of a single channel. That is, the multi-cast packet transmitted from the digital broadcast server to the IP network contains only one single program transport stream (SPTS) MPEG-2 TS.
If there is a channel change request from a user, the set-top box accesses the requested channel and provides the digital television with the digital broadcast data obtained by decoding the packets received over the corresponding channel. That is, the set-top box interprets a program association table (PAT) contained in the packet received over the changed channel to obtain program map table (PMT) information, and perceives a video program identification (PID) contained in the obtained PMT information. Then, the set-top box finds packets corresponding to the video PID perceived through the packet received over the changed channel from the MPEG-2 TS and decodes them.
However, it takes time for the set-top box to interpret the PAT to obtain the PMT information and perceive the PID information from the obtained PMT information. Thus there is an inconvenient channel change delay.